JP3647218B2

JP3647218B2 - Air zinc battery

Info

Publication number: JP3647218B2
Application number: JP23390997A
Authority: JP
Inventors: 浩史渡部; 真智大橋; 秀之小方; 正夫川口
Original assignee: Toshiba Battery Co Ltd
Current assignee: FDK Twicell Co Ltd
Priority date: 1997-08-29
Filing date: 1997-08-29
Publication date: 2005-05-11
Anticipated expiration: 2017-08-29
Also published as: JPH1173949A

Description

【０００１】
【発明の属する技術分野】
本発明は空気亜鉛電池の高容量化に関する。
【０００２】
【従来の技術】
亜鉛を負極作用物質とし、空気中の酸素を正極作用物質とする空気亜鉛電池は、通常の電池に比べ、正極作用物質を電池内に詰め込む必要がないために、負極作用物質である亜鉛をより多く詰め込むことが可能で、アルカリマンガン電池や酸化銀電池に比較して大容量が得られるという特徴があり、需要が拡大してきている。
【０００３】
また、空気亜鉛電池は、環境問題が提起された水銀電池と互換性があるので、その代替とされており、その主用途である補聴器に使用されている。そして電池交換の頻度をより少なくすることが望まれており、近年一層高容量化の要望が高まっている。
【０００４】
【発明が解決しようとする課題】
ところで、空気亜鉛電池を高容量化するためには、ゲル状亜鉛負極の放電利用率を向上させるか、あるいは作用物質としての亜鉛をより多く充填して理論的な容量を増やす必要がある。
【０００５】
しかしながら、正極作用物質を充填しなくともよいとはいえ、内容積には限界があるので、亜鉛の増量には限界がある。また、亜鉛は放電反応後に反応生成物となって体積が膨張するために、内容積一杯までにゲル状亜鉛負極を充填すると、過放電状態になったときに、膨張した負極生成物によってアルカリ電解液が押し出され、空気孔から漏液するという問題がある。
【０００６】
充填するゲル状亜鉛負極の体積を増やさずに亜鉛量を増やすためには、アルカリ電解液を減らし、亜鉛を増やしたゲル状亜鉛負極の配合組成にすればよいが、アルカリ電解液量が減少すると、亜鉛の放電利用率が悪化する傾向にあり、亜鉛を増加した分だけ高容量化を実現するのは困難である。
【０００７】
逆に、亜鉛の放電利用率の向上のためには、アルカリ電解液比率のより高いゲル状亜鉛負極を使用することが考えられるが、もともと空気亜鉛電池の亜鉛の放電利用率は９０％以上もあり、放電利用率の向上による大幅な高容量化は望めない。さらにアルカリ電解液を増やした分、一定容積に充填される亜鉛量は減少するので、結果的に高容量化は達成できない。
本発明は、このような問題を解決するためになされたもので、その目的は、過放電後の漏液を生ずることなく空気亜鉛電池をより高容量化することにある。
【０００８】
【課題を解決するための手段】
この目的を達成するため、本研究者らが鋭意研究の結果、ゲル状亜鉛負極の配合組成、負極容積に対するゲル状亜鉛負極体積の充填率を適正化することにより、過放電後の漏液が生ずることなく、より高容量化を達成することができることがわかった。
【０００９】
すなわち、本発明は、空気中の酸素を正極作用物質とし、負極集電体を兼ねた負極容器に亜鉛合金粉，アルカリ電解液，及びゲル化剤で構成されたゲル状亜鉛負極を有する空気亜鉛電池において、前記ゲル状亜鉛負極の配合組成が亜鉛合金粉１００重量部に対してアルカリ電解液が２０〜２５重量部であり、且つ負極容積に対する前記ゲル状亜鉛負極の充填率が８５〜９０％であることを特徴とする。
【００１０】
従来の空気亜鉛電池では、ゲル状亜鉛負極の配合組成は亜鉛合金粉１００重量部に対してアルカリ電解液が２５〜３０重量部程度が普通であるが、これ以上亜鉛合金粉の配合比率を増やしアルカリ電解液を減らすと、亜鉛の放電利用率が低下してしまう。これに対し本発明の空気亜鉛電池では、ゲル状亜鉛負極の配合組成が亜鉛合金粉１００重量部に対してアルカリ電解液が２０〜２５重量部であるが、ゲル状亜鉛負極体積の充填率を８５〜９０％とすることで、放電利用率の低下が最小に防げることがわかった。
【００１１】
すなわち、このようなゲル状亜鉛負極の充填率であれば、ゲル状亜鉛負極と負極集電体やセパレータとの接触が最適になり、放電利用率を良好に保てる。ゲル状亜鉛負極の充填率が８５％未満であると前述の接触が悪化し、放電利用率も低下してしまう。９０％以上になると放電中に正極触媒を圧迫して放電に悪影響を及ぼす。
【００１２】
また、過放電後の漏液の発生は、ゲル状亜鉛負極の配合組成及び充填率と密接に関係しており、アルカリ電解液の比率が高いゲル状亜鉛負極ほど同じ充填率でも漏液が発生し易くなる。そして放電生成物の体積が負極内容積に占める比率Ｍ（占拠率、％）は次式（１）で求められ、これを１１０％程度以下にするのがよい。本発明のゲル状亜鉛負極の配合組成及び充填率の範囲であれば、占拠率Ｍは１１２％以下となり、漏液は発生しない。この点からもゲル状亜鉛負極の配合組成及び充填率は、本発明の範囲が妥当である。
【００１３】
【数１】

【００１４】
なお、Ｇａは次の式から求めた。
Ｇａ＝［放電に利用された亜鉛の体積］×０．５８７
０．５８７は、放電利用率が一番良い電流密度（ｍＡ／ｍｍ²）で放電し、放電生成物が酸化亜鉛になると仮定したときの、放電後亜鉛の体積増加率で、
亜鉛：比重７．１４，原子量６５．３
酸化亜鉛：比重５．６，分子量８１．３
を用いて次式のように計算した。
０．５８７＝［（８１．３／５．６）／（６５．３／７．１４）］−１＝１．５８７−１
【００１５】
【発明の実施の形態】
（ゲル状亜鉛負極の調製）
ゲル状亜鉛負極は、亜鉛合金粉，アルカリ電解液及びゲル化剤としてのポリアクリル酸で構成される。亜鉛合金粉とアルカリ電解液の配合組成は、表１に示すように、亜鉛合金粉１００重量部に対して、３０ｗｔ％水酸化カリウム水溶液を３２．５，３０．０，２７．５，２５．０，２２．５，２０．０及び１７．５重量部の７種類とした。ゲル状亜鉛負極は、まず亜鉛合金粉とポリアクリル酸（３０ｗｔ％水酸化カリウム水溶液１００重量部に対して１．６重量部）をドライ撹拌し、その後水酸化カリウム水溶液と共にウェット撹拌して調製した。
また、７種類のゲル状亜鉛負極の比重を、亜鉛合金粉の比重７．１４と、３０ｗｔ％水酸化カリウム水溶液の比重１．２９とを用いて算出し、表１に示した。
【００１６】
【表１】

【００１７】
（実施例１〜６）
配合組成として、亜鉛合金粉１００重量部に対して、３０ｗｔ％水酸化カリウム水溶液を２５．０，２２．５及び２０．０重量部の３種類のゲル状亜鉛負極を使用し、ゲル状亜鉛負極の充填率を８５及び９０％として、図１に示すようなＰＲ４４型空気亜鉛電池を作製した。
【００１８】
図１において、１は負極集電体、２はゲル状亜鉛負極、３はセパレータ、４はパッキング、５は正極触媒、６は正極缶、７はテフロン膜、８は空気拡散紙、９は空気孔、１０は絶縁シートである。
【００１９】
ゲル状亜鉛負極の充填率は、次のようにしてゲル状亜鉛負極の重量で調整した。まず電池の形状寸法より負極内容積３０７μｌを算出し、各々の充填率８５及び９０％に対応する体積を求め、次にそれらの体積を各々３種類のゲル状亜鉛負極の比重を用いて重量に換算した。
【００２０】
このとき正極触媒は、マンガン酸化物，活性炭及びテフロン粉末を混合撹拌して得られた正極合剤をシート状に圧延し、片面にニッケルメッキしたステンレスネットを、他面にテフロン膜をそれぞれ圧着して得られた。また、パッキングはナイロン製パッキングを使用した。
【００２１】
負極ケースを兼ねた負極集電体はニッケル−ステンレス−銅の３層クラッド材を成形加工して使用した。
正極ケースは、鉄材を成形加工した後にニッケルメッキを施して使用した。
【００２２】
（比較例１〜２２）
実施例と同様にして、配合組成が、亜鉛合金粉１００重量部に対して、３０ｗｔ％水酸化カリウム水溶液を３２．５，３０．０，２７．５，２５．０，２２．５，２０．０及び１７．５重量部の７種類のゲル状亜鉛負極を使用し、ゲル状亜鉛負極の充填率を８０，８５，９０及び９５％として、図１に示すようなＰＲ４４型空気亜鉛電池を作製した。また、ゲル状亜鉛負極の充填率は、実施例と同様にゲル状亜鉛負極の重量で調整した。
【００２３】
（評価）
上記実施例及び比較例の電池の各２０個について、６２０Ω及び２５０Ωの連続放電試験を行った。６２０Ω連続放電は、ＰＲ４４型空気亜鉛電池では、正負極の対向面積に対して０．０２５ｍＡ／ｍｍ²程度の放電になり放電利用率が比較的良い条件である。２５０Ω連続放電は、０．０５ｍＡ／ｍｍ²程度の比較的重負荷の放電である。表１に結果を示す。各数値は、２０個の電池の平均値である。
【００２４】
次に、実施例及び比較例の電池各２０個を２５℃−８５％ＲＨの環境下において、６２０Ωで５００時間放電し、過放電後の空気孔からの漏液を目視調査した。ＰＲ４４型空気亜鉛電池の６２０Ω連続放電は、２００〜３５０時間程度で放電が終わるので、１．５〜２．５倍程度の過放電である。空気亜鉛電池では、過放電により負極内容物が膨張したときに空気孔からアルカリ電解液が押し出されて漏液することがあり、２５℃−８５％ＲＨのように高湿の環境下では特に漏液しやすくなる。
結果を表１に示す。各数値は、電池２０個中の漏液した電池の個数である。
【００２５】
この表から明らかなように、ゲル状亜鉛負極の配合組成に関わらず、充填率が８５％から８０％に減少すると放電利用率が大きく低下し高容量化できない。充填率が８５％から９０％に増加すると、本発明の場合は過放電後の漏液特性は悪くならないが、比較例の場合は漏液特性が悪化する。配合組成が亜鉛合金粉１００重量部に対してアルカリ電解液が３２．５，３０．０，２７．５及び１７．５重量部のゲル状亜鉛負極の場合は、充填率を８５及び９０％にしても高容量化と過放電後の漏液特性の両方を満足させるものはない。
【００２６】
以上のように、ゲル状亜鉛負極の配合組成が、亜鉛合金粉１００重量部に対してアルカリ電解液２０〜２５重量部であり、電池の負極容積に対してゲル状亜鉛負極体積の充填率が８５〜９０％である本発明品は、従来の空気亜鉛電池に比較して、高容量化することができ、且つ過放電後の漏液の危険性もない。
【００２７】
なお、本発明は上記実施例により限定されるものではなく、本発明に直接影響を及ぼさない、亜鉛合金粉，ゲル化剤，電解液濃度，正極触媒等の要素については本発明の範囲を逸脱しない限り、変更して差支えない。
【００２８】
【発明の効果】
以上説明したように、本発明によれば、従来の空気亜鉛電池に比較して、高容量化され、且つ過放電漏液の危険性もない電池を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施例であるＰＲ４４型空気亜鉛電池の断面図。
【符号の説明】
１…負極集電体、２…ゲル状亜鉛負極、３…セパレータ、４…パッキング、５…正極触媒、６…正極缶、７…テフロン膜、８…空気拡散紙、９…空気孔、１０…絶縁シート。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to increasing the capacity of a zinc-air battery.
[0002]
[Prior art]
The zinc-air battery, which uses zinc as the negative electrode active substance and oxygen in the air as the positive electrode active substance, does not require the positive electrode active substance to be packed in the battery as compared with a normal battery. It can be packed in large quantities, and has a feature that a large capacity can be obtained as compared with alkaline manganese batteries and silver oxide batteries, and the demand is increasing.
[0003]
In addition, since the zinc-air battery is compatible with the mercury battery in which environmental problems have been raised, it is used as a substitute for it, and is used in hearing aids, which are its main application. Further, it is desired to reduce the frequency of battery replacement, and in recent years there has been an increasing demand for higher capacity.
[0004]
[Problems to be solved by the invention]
By the way, in order to increase the capacity of the air zinc battery, it is necessary to improve the discharge utilization of the gelled zinc negative electrode or to increase the theoretical capacity by filling more zinc as an active substance.
[0005]
However, although there is no need to fill the positive electrode active substance, there is a limit to the amount of zinc because there is a limit to the internal volume. In addition, since zinc becomes a reaction product after the discharge reaction and the volume expands, when the gelled zinc negative electrode is filled up to the full inner volume, it becomes alkaline electrolysis by the expanded negative electrode product when overdischarge occurs. There is a problem that the liquid is pushed out and leaks from the air hole.
[0006]
In order to increase the amount of zinc without increasing the volume of the gelled zinc negative electrode to be filled, the alkaline electrolyte is reduced and the composition of the gelled zinc negative electrode with increased zinc may be used. The zinc discharge utilization rate tends to deteriorate, and it is difficult to increase the capacity by the amount of zinc.
[0007]
On the other hand, in order to improve the discharge utilization rate of zinc, it is conceivable to use a gelled zinc negative electrode having a higher alkaline electrolyte ratio, but the zinc discharge utilization rate of the zinc-air battery is originally over 90%. There is no significant increase in capacity due to improved discharge utilization. Furthermore, since the amount of zinc filled in a certain volume decreases as the alkaline electrolyte is increased, the increase in capacity cannot be achieved as a result.
The present invention has been made to solve such a problem, and an object thereof is to increase the capacity of the air zinc battery without causing leakage after overdischarge.
[0008]
[Means for Solving the Problems]
In order to achieve this purpose, as a result of diligent research conducted by the present researchers, by adjusting the composition ratio of the gelled zinc negative electrode and the filling rate of the gelled zinc negative electrode volume with respect to the negative electrode volume, the leakage after overdischarge is reduced. It has been found that higher capacity can be achieved without the occurrence.
[0009]
That is, the present invention relates to an air zinc having a gelled zinc negative electrode composed of a zinc alloy powder, an alkaline electrolyte, and a gelling agent in a negative electrode container having oxygen in the air as a positive electrode active substance and also serving as a negative electrode current collector. In the battery, the composition ratio of the gelled zinc negative electrode is 20 to 25 parts by weight of the alkaline electrolyte with respect to 100 parts by weight of the zinc alloy powder, and the filling rate of the gelled zinc negative electrode with respect to the negative electrode volume is 85 to 90%. It is characterized by being.
[0010]
In a conventional air zinc battery, the composition ratio of the gelled zinc negative electrode is usually about 25 to 30 parts by weight of the alkaline electrolyte with respect to 100 parts by weight of the zinc alloy powder, but the blending ratio of the zinc alloy powder is further increased. If the alkaline electrolyte is reduced, the discharge efficiency of zinc will decrease. On the other hand, in the air zinc battery of the present invention, the composition ratio of the gel-like zinc negative electrode is 20 to 25 parts by weight of the alkaline electrolyte with respect to 100 parts by weight of the zinc alloy powder. It turned out that the fall of a discharge utilization factor can be prevented to the minimum by setting it as 85 to 90%.
[0011]
That is, with such a filling rate of the gelled zinc negative electrode, the contact between the gelled zinc negative electrode and the negative electrode current collector or the separator becomes optimal, and the discharge utilization rate can be kept good. If the filling rate of the gelled zinc negative electrode is less than 85%, the aforementioned contact deteriorates and the discharge utilization rate also decreases. If it is 90% or more, the positive electrode catalyst is pressed during discharge, which adversely affects the discharge.
[0012]
In addition, the occurrence of liquid leakage after overdischarge is closely related to the composition and filling rate of the gelled zinc negative electrode. It becomes easy to do. The ratio M (occupancy rate,%) of the volume of the discharge product to the negative electrode internal volume is obtained by the following equation (1), and it is preferable to set this to about 110% or less. If it is the range of the compounding composition and filling rate of the gelatinous zinc negative electrode of this invention, the occupation rate M will be 112% or less, and a liquid leak will not generate | occur | produce. Also from this point, the range of the present invention is appropriate for the composition and filling rate of the gelled zinc negative electrode.
[0013]
[Expression 1]

[0014]
Ga was obtained from the following equation.
Ga = [volume of zinc used for discharge] × 0.587
0.587 is the volume increase rate of zinc after discharge when it is assumed that discharge is performed at a current density with the best discharge utilization rate (mA / mm ² ) and the discharge product is zinc oxide.
Zinc: specific gravity 7.14, atomic weight 65.3
Zinc oxide: specific gravity 5.6, molecular weight 81.3
Was calculated as follows.
0.587 = [(81.3 / 5.6) / (65.3 / 7.14)]-1 = 1.587-1
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(Preparation of gelled zinc negative electrode)
The gelled zinc negative electrode is composed of zinc alloy powder, an alkaline electrolyte, and polyacrylic acid as a gelling agent. As shown in Table 1, the blending composition of the zinc alloy powder and the alkaline electrolyte is 32.5, 30.0, 27.5, 25, 30 wt% potassium hydroxide aqueous solution with respect to 100 parts by weight of the zinc alloy powder. Seven types of 0, 22.5, 20.0, and 17.5 parts by weight were used. The gelled zinc negative electrode was prepared by first dry-stirring zinc alloy powder and polyacrylic acid (1.6 parts by weight with respect to 100 parts by weight of 30 wt% potassium hydroxide aqueous solution) and then wet-stirring with the potassium hydroxide aqueous solution. .
The specific gravity of the seven kinds of gelled zinc negative electrodes was calculated using the specific gravity of 7.14 of the zinc alloy powder and the specific gravity of 1.29 of the 30 wt% potassium hydroxide aqueous solution.
[0016]
[Table 1]

[0017]
(Examples 1-6)
As a blending composition, 3 types of gelled zinc negative electrodes of 25.0, 22.5 and 20.0 parts by weight of 30 wt% potassium hydroxide aqueous solution are used with respect to 100 parts by weight of zinc alloy powder. The PR44 type zinc-air battery as shown in FIG.
[0018]
In FIG. 1, 1 is a negative electrode current collector, 2 is a gel-like zinc negative electrode, 3 is a separator, 4 is packing, 5 is a positive electrode catalyst, 6 is a positive electrode can, 7 is a Teflon film, 8 is air diffusion paper, and 9 is air. The holes 10 are insulating sheets.
[0019]
The filling rate of the gelled zinc negative electrode was adjusted by the weight of the gelled zinc negative electrode as follows. First, the negative electrode internal volume of 307 μl is calculated from the battery geometry, and the volume corresponding to each filling rate of 85 and 90% is obtained, and then these volumes are converted into weights using the specific gravity of each of the three types of gelled zinc negative electrodes. Converted.
[0020]
At this time, the positive electrode catalyst was prepared by rolling and mixing a positive electrode mixture obtained by mixing and stirring manganese oxide, activated carbon and Teflon powder into a sheet, and bonding a stainless steel net plated with nickel on one side and a Teflon film on the other side. Obtained. The packing used was a nylon packing.
[0021]
A negative electrode current collector also serving as a negative electrode case was formed by forming a nickel-stainless-copper three-layer clad material.
The positive electrode case was used after being nickel-plated after an iron material was molded.
[0022]
(Comparative Examples 1 to 22)
In the same manner as in the examples, the blending composition was 32.5, 30.0, 27.5, 25.0, 22.5, 20. Using 7 types of gelled zinc negative electrodes of 0 and 17.5 parts by weight, and filling the gelled zinc negative electrode with 80, 85, 90 and 95%, a PR44 type air zinc battery as shown in FIG. 1 was produced. did. The filling rate of the gelled zinc negative electrode was adjusted by the weight of the gelled zinc negative electrode in the same manner as in the example.
[0023]
(Evaluation)
A continuous discharge test of 620Ω and 250Ω was performed on each of the 20 batteries of the examples and comparative examples. The 620Ω continuous discharge is a condition in which the discharge efficiency is relatively good in the PR44 type zinc-air battery because the discharge is about 0.025 mA / mm ^{2 with} respect to the facing area of the positive and negative electrodes. The 250Ω continuous discharge is a relatively heavy load discharge of about 0.05 mA / mm ² . Table 1 shows the results. Each numerical value is an average value of 20 batteries.
[0024]
Next, 20 batteries of each of Examples and Comparative Examples were discharged at 620Ω for 500 hours in an environment of 25 ° C. to 85% RH, and the leakage from the air holes after overdischarge was visually inspected. The 620Ω continuous discharge of the PR44 type zinc-air battery is overdischarge of about 1.5 to 2.5 times since the discharge is completed in about 200 to 350 hours. In a zinc-air battery, when the negative electrode contents expand due to overdischarge, the alkaline electrolyte may be pushed out from the air holes and leak, and this is particularly noticeable in high humidity environments such as 25 ° C.-85% RH. Easy to liquid.
The results are shown in Table 1. Each numerical value is the number of leaked batteries in 20 batteries.
[0025]
As is apparent from this table, regardless of the composition of the gelled zinc negative electrode, when the filling rate is reduced from 85% to 80%, the discharge utilization rate is greatly reduced and the capacity cannot be increased. When the filling rate is increased from 85% to 90%, the leakage characteristics after overdischarge are not deteriorated in the case of the present invention, but the leakage characteristics are deteriorated in the case of the comparative example. In the case of a gelled zinc negative electrode having a blending composition of 32.5, 30.0, 27.5 and 17.5 parts by weight with respect to 100 parts by weight of zinc alloy powder, the filling rate should be 85 and 90%. However, there is nothing that satisfies both high capacity and leakage characteristics after overdischarge.
[0026]
As described above, the composition ratio of the gelled zinc negative electrode is 20 to 25 parts by weight of the alkaline electrolyte with respect to 100 parts by weight of the zinc alloy powder, and the filling rate of the gelled zinc negative electrode volume with respect to the negative electrode volume of the battery is The product of the present invention, which is 85 to 90%, can have a higher capacity than the conventional air zinc battery, and there is no risk of leakage after overdischarge.
[0027]
It should be noted that the present invention is not limited to the above-described embodiments, and elements such as zinc alloy powder, gelling agent, electrolyte concentration, and positive electrode catalyst that do not directly affect the present invention depart from the scope of the present invention. It can be changed as long as it is not.
[0028]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a battery having a higher capacity and no risk of overdischarge leakage as compared with a conventional air zinc battery.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a PR44 type zinc-air battery that is one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Negative electrode collector, 2 ... Gel-like zinc negative electrode, 3 ... Separator, 4 ... Packing, 5 ... Positive electrode catalyst, 6 ... Positive electrode can, 7 ... Teflon membrane, 8 ... Air diffusion paper, 9 ... Air hole, 10 ... Insulating sheet.

Claims

In the air zinc battery having a gelled zinc negative electrode composed of a zinc alloy powder, an alkaline electrolyte, and a gelling agent in a negative electrode container having oxygen in the air as a positive electrode active substance and also serving as a negative electrode current collector, The composition of the zinc negative electrode is 20 to 25 parts by weight of the alkaline electrolyte with respect to 100 parts by weight of the zinc alloy powder, and the filling rate of the gelled zinc negative electrode with respect to the negative electrode volume is 85 to 90%. Air zinc battery.